Semiconductor ceramic composition, method for producing same, ptc element and heat generating module

Abstract

There is provided a semiconductor ceramic composition in which a portion of Ba of BaTiO 3 is substituted by Bi—Na, which exhibits an excellent jump characteristic while reducing room temperature resistivity and which also reduces room temperature resistivity and exhibits small change with time. A semiconductor ceramic composition which is represented by a composition formula of [(Bi θ —Na δ ) x (Ba 1-y R y ) 1-x ]TiO 3 (where R is at least one kind of rare earth elements), in which x, y, θ and δ satisfy 0<x≦0.3, 0<y≦0.02, 0.46<θ≦0.62 and 0.45≦δ≦0.60 and a molar ratio Bi/Na of Bi to Na in a sintered body is more than 1.02 but 1.20 or less, is provided. Also, a method for producing a semiconductor ceramic composition containing a means for performing weighing such a manner that the molar ratio Bi/Na of Bi to Na is 1.05 to 1.24 so that an amount of Bi in a Bi raw material powder becomes larger than an amount of Na in an Na raw material powder at preparation of a (BiNa)TiO 3 calcined powder or a means for adding a Bi raw material powder at preparation of a mixed calcined powder to perform adjustment so that the molar ratio Bi/Na is 1.04 to 1.23, in order that the molar ratio Bi/Na of Bi to Na in a sintered body becomes more than 1.02 but 1.20 or less.

1 . A semiconductor ceramic composition which is represented by a composition formula of [(Bi θ —Na δ ) x (Ba 1-y R y ) 1-x ]TiO 3  (wherein R is at least one kind of rare earth elements), wherein x, y, θ and δ satisfy 0<x≦0.3, 0<y≦0.02, 0.46<θ≦0.62 and 0.45≦δ≦0.60 and a molar ratio Bi/Na of Bi to Na in a sintered body is more than 1.02 but 1.20 or less. 
     
     
         2 . A semiconductor ceramic composition which is represented by a composition formula of [(Bi θ —Na δ ) x Ba 1-x ][Ti 1-z M z ]O 3  (wherein M is at least one kind of Nb, Ta and Sb), wherein x, z, θ and δ satisfy 0<x≦0.3, 0<z≦0.0050, 0.46<θ≦0.62 and 0.45≦δ≦0.60 and a molar ratio Bi/Na of Bi to Na in a sintered body is more than 1.02 but 1.20 or less. 
     
     
         3 - 10 . (canceled) 
     
     
         11 . The semiconductor ceramic composition according to  claim 1 , wherein a change with time is 10% or less at the time when an electrification is performed at 13 V for 5000 hours per a thickness of 1 mm in an electrification direction of the semiconductor ceramic composition. 
     
     
         12 . The semiconductor ceramic composition according to  claim 2 , wherein a change with time is 10% or less at the time when an electrification is performed at 13 V for 5000 hours per a thickness of 1 mm in an electrification direction of the semiconductor ceramic composition. 
     
     
         13 . A method for producing a semiconductor ceramic composition comprising:
 a step of preparing a (BaR)TiO 3  calcined powder (wherein R is at least one kind of rare earth elements) and a (Bi o -N calcined powder separately,   a step of obtaining a formed body composed of a mixed calcined powder obtained by mixing the (BaR)TiO 3  calcined powder and the (Bi θ —Na δ )TiO 3  calcined powder, and   a step of sintering the formed body in a non-oxidative atmosphere having an oxygen concentration of 1 vol % or less to make a sintered body,   wherein, in order that θ and δ in the sintered body satisfy 0.46<θ≦0.62 and 0.45≦δ≦0.60 and a molar ratio Bi/Na of Bi to Na becomes more than 1.02 but 1.20 or less, in the step of preparing the (Bi θ —Na δ )TiO 3  calcined powder, weighing is performed such a manner that weighed values of θ and δ satisfy 0.49<θ≦0.66 and 0.46<δ≦0.62 and the molar ratio Bi/Na of Bi to Na is 1.05 to 1.24 so that an amount of Bi in a Bi raw material powder becomes larger than an amount of Na in an Na raw material powder.   
     
     
         14 . A method for producing a semiconductor ceramic composition comprising:
 a step of preparing a Ba(TiM)O 3  calcined powder (wherein M is at least one kind of Nb, Ta and Sb) and a (Bi θ —Na δ )TiO 3  calcined powder separately,   a step of obtaining a formed body composed of a mixed calcined powder obtained by mixing the Ba(TiM)O 3  calcined powder and the (Bi θ —Na δ )TiO 3  calcined powder, and   a step of sintering the formed body in a non-oxidative atmosphere having an oxygen concentration of 1 vol % or less to make a sintered body,   wherein, in order that θ and δ in the sintered body satisfy 0.46<θ≦0.62 and 0.45≦δ≦0.60 and a molar ratio Bi/Na of Bi to Na becomes more than 1.02 but 1.20 or less, in the step of preparing the (Bi θ —Na δ )TiO 3  calcined powder, weighing is performed such a manner that weighed values of θ and δ satisfy 0.49<θ≦0.66 and 0.46<δ≦0.62 and the molar ratio Bi/Na of Bi to Na is 1.05 to 1.24 so that an amount of Bi in a Bi raw material powder becomes larger than an amount of Na in an Na raw material powder.   
     
     
         15 . The method for producing a semiconductor ceramic composition according to  claim 13 , wherein, at the preparation of the mixed calcined powder, a Bi raw material powder is added to perform adjustment so that the weighed values of θ and δ satisfy 0.49<θ≦0.66 and 0.46<δ≦1.62. 
     
     
         16 . The method for producing a semiconductor ceramic composition according to  claim 14 , wherein, at the preparation of the mixed calcined powder, a Bi raw material powder is added to perform adjustment so that the weighed values of θ and δ satisfy 0.49<θ≦0.66 and 0.46<δ≦0.62. 
     
     
         17 . A method for producing a semiconductor ceramic composition comprising:
 a step of preparing a (BaR)TiO 3  calcined powder (wherein R is at least one kind of rare earth elements) and a (Bi θ —Na δ )TiO 3  calcined powder separately,   a step of obtaining a formed body composed of a mixed calcined powder obtained by mixing the (BaR)TiO 3  calcined powder and the (Bi θ —Na δ )TiO 3  calcined powder, and   a step of sintering the formed body in a non-oxidative atmosphere having an oxygen concentration of 1 vol % or less to make a sintered body,   wherein, in order that θ and δ in the sintered body satisfy 0.46<θ≦0.62 and 0.45≦δ≦0.60 and a molar ratio Bi/Na of Bi to Na becomes more than 1.02 but 1.20 or less, a Bi raw material powder is added at the preparation of the mixed calcined powder to perform adjustment so that weighed values of θ and δ satisfy 0.48<θ≦0.65 and 0.45≦δ≦0.62 and a molar ratio Bi/Na of Bi to Na is 1.04 to 1.23.   
     
     
         18 . A method for producing a semiconductor ceramic composition comprising:
 a step of preparing a Ba(TiM)O 3  calcined powder (wherein M is at least one kind of Nb, Ta and Sb) and a (Bi θ —Na δ )TiO 3  calcined powder separately,   a step of obtaining a formed body composed of a mixed calcined powder obtained by mixing the Ba(TiM)O 3  calcined powder and the (Bi θ —Na δ )TiO 3  calcined powder, and   a step of sintering the formed body in a non-oxidative atmosphere having an oxygen concentration of 1 vol % or less to form a sintered body,   wherein, in order that 0 and 8 in the sintered body satisfy 0.46<θ≦0.62 and 0.45≦δ≦0.60 and a molar ratio Bi/Na of Bi to Na becomes more than 1.02 but 1.20 or less, a Bi raw material powder is added at the preparation of the mixed calcined powder to perform adjustment so that weighed values of θ and δ satisfy 0.48<θ≦0.65 and 0.45≦δ≦0.62 and the molar ratio Bi/Na of Bi to Na is 1.04 to 1.23.   
     
     
         19 . A PTC element comprising the semiconductor ceramic composition according to  claim 1  and provided thereon an ohmic electrode for passing an electric current though the semiconductor ceramic composition. 
     
     
         20 . A PTC element comprising the semiconductor ceramic composition according to  claim 2  and provided thereon an ohmic electrode for passing an electric current though the semiconductor ceramic composition. 
     
     
         21 . A heat generating module comprising the PTC element according to  claim 19  and a power supplying electrode provided on the PTC element. 
     
     
         22 . A heat generating module comprising the PTC element according to  claim 20  and a power supplying electrode provided on the PTC element.